To clear up confusion over whether the ring was simply a Christmas gift, Hefner later tweeted: "Yes, the ring I gave Crystal is an engagement ring. I didn't mean to make a mystery out of it. A very merry Christmas to all."

This would be the third marriage for the 84-year-old, star of E! reality series "The Girls Next Door," which chronicles Hefner's life at the Playboy Mansion. He divorced Playmate Kimberly Conrad last year.